19.6.1 Callbacks to update the display pane

One main function,
update-selection
, serves to update the display pane whenever selections are made in the graph pane or the list panel.

(defun update-selection (type data interface)

(setf (capi:display-pane-text (selection-reader interface))

(format nil "~A ~A" data type)))

The following three functions are the callbacks specified whenever a select, retract or extend action is performed in either the list panel or the graph pane. Each function is named according to the type of callback it is used for, and it simply calls
update-selection
with an additional argument denoting the callback type.